Results of a study with over 13 years of follow-up were recently published in Nature Communications, detailing many of the associations between physical activity and fat accumulation in children aged 11 to 24. Data from the UK-based Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort provided a longitudinal analysis of accelerometer-assessed movement and its relationship to body composition (measured by DEXA) among children, the largest and longest to date. It included an examination of potential mediating factors (e.g., glucose, insulin, etc.), and is a significant step toward establishing causality between lack of movement and accumulation of fat mass.
The study included movement and body composition data from over 6,000 children recorded at ages 11, 15, and 24. This included accelerometer data that captured between 4 to 7 days of consecutive use (worn for at least 10 hours per day), body composition as assessed by DEXA, and fasting blood samples of glucose, insulin, hs-CRP, LDL-C, HDL-C, and triglycerides. There is much to learn from this study, but some key takeaways:
- Sedentary time (ST) increased from 6 to 9 hours per day during the transition from childhood to young adulthood, associated with an increase in total and truncal fat mass. Each minute per day of ST was associated with a 1.3g increase in total fat mass, with associations partly mediated by a decrease in lipoprotein lipase and an increase in insulin.
- Light physical activity (LPA) also decreased from 9 to 6 hours during this transition. Each minute per day of LPA was associated with a 3.6g decrease in total fat mass, while each minute per day of moderate to vigorous physical activity (MVPA) was associated with a 1.3 g decrease in total fat mass. Some of these associations may be in part mediated by insulin and LDL-C.
- While both types of activity are important, LPA may be an underappreciated target to prevent fat accumulation: Adding 3-4 hours per day of LPA may lower total fat mass ten times more than 60 min/day of MVPA.